1. Field of the Invention
The invention relates to apparatus for metering of electric energy on a time-of-use basis and, more particularly, to improved apparatus for programming electric energy meters.
2. Description of the Prior Art
Electric utilities must provide sufficient generating capacity to meet peak energy requirements present during periods of highest demand. Thus, a large disparity in load between peak and off-peak periods results in expensive generating capacity remaining idle for a portion of the time. The more a utility can smooth its total customer demand over time, the more efficiently can generating resources be utilized. An increasingly popular method for smoothing load is to be set the cost of electric energy at a higher rate during periods of peak energy demand and at a lower rate during off-peak periods, thereby providing an incentive for customers to shift their usage from peak periods to off-peak periods.
To generate a customer's monthly bill using this system, it is necessary to measure the amount of electricity consumed at a plurality of billing rates, with different rates being in effect at different times depending upon whether the time of consumption is a peak-load period, a non-peak load period, a weekend, holiday, etc. This type of system is known as time-of-use metering. Time registering programmable AC electric energy meters suitable for time-of-use applications require replaceable and alterable meter control data so that the meter may be programmed for various measurement or billing rate schedules on a time and date basis. Apparatus for programming such meters is disclosed in U.S. Pat. No. 4,291,375.
As more experience is gained with time-of-use metering, more and more sophisticated and complex rate schedules are being implemented. Utilities are also requiring more data to be accumulated by a customer's meter. Examples of these increased requirements are the time and date of maximum demand for energy during each rate period; the value, time, and date of the highest demand; and the ability to automatically store all rate period billing data at the end of the billing period.
The programming of information into a customer's meter presents conflicting requirements. On the one hand, it is desirable that the utilities be able to formulate the rate schedules and advanced data retrieval features in a convenient and easily implemented fashion. On the other hand, the actual device which will be used by field personnel to enter the required data into the customer's meters must be small, portable, and easy to use. Furthermore, it should be capable of programming various types of registers. Apparatus available in the prior art has not been found sufficient to meet these requirements.